1. Field of the Invention
The present invention relates to improved apparatus for fabricating semiconductor devices having a nozzle and a spin chuck, and more particularly, to an apparatus with a cover, spaced apart from and confronting the wafer surface, for protecting wafers from solutions used to fabricate the semiconductor devices.
2. Description of the Related Art
Generally, semiconductor devices are created by depositing various insulating or metallic layers on a semiconductor wafer to form a multiple layer structure. Desired circuit patterns are formed on the layers according to the properties of the respective semiconductor devices.
The circuit patterns are formed by photolithography processes, which generally comprise coating a photoresist on the wafer, aligning a photo mask having the circuit pattern formed thereon with the wafer, and then exposing selected areas of the photoresist consistent with the pattern. The exposed portion of the photoresist is removed using a developing solution so as to form a photoresist pattern. Thereafter, an etching process is performed using the photoresist pattern as an etching mask to thereby form the desired circuit pattern.
During the photolithography process, specific solutions (e.g., solutions used in the semiconductor device fabrication process or developing solutions) are sprayed onto the substrate using a nozzle and a spin chuck as shown in FIG. 1. The spin chuck 12 secures the wafer W thereon, usually via vacuum suction, and rotates it at a specific speed. A specific solution 13 is sprayed through the nozzle 14 and onto the wafer W surface. More than one nozzle 14 may be provided, and the nozzle locations may be varied according to the process steps and operating conditions.
As the solution 13 is sprayed through the nozzle 14, the wafer W is rotated by rotating the spin chuck 12, so that the solution 13 is uniformly dispersed or coated along the entire wafer surface. However, as the solution 13 reaches the edge portion of the wafer W, it is scattered due to the centrifugal force of the rotating wafer W.
A bowl 18, provided inside a process chamber 16, surrounds the spin chuck 12, nozzle 14, and wafer W, to prevent the solution 13 supplied onto the wafer W from being scattered onto the inner wall of the process chamber 16. However, some of the solution 13 contacting the bowl 18 is undesirably reflected back onto the wafer W, as shown by the arrows in FIG. 1, which serves as a source for particle generation. The unwanted solution 13 reflected from the bowl 18 may cause pattern bridges and profile failures during the formation of the pattern. Such defects require the wafer W to be rejected or reworked, thereby resulting in a reduction in productivity.
To minimize the unwanted reflected solution, conventional procedures seek to precisely control the process parameters, such as the viscosity of the solution 13 or the rotation speed of the spin chuck 12. However, such process control parameters must take into account the desired parameters of the overall fabrication process, and as such, the process control ranges are limited.